Trivalent antimony catalyst

ABSTRACT

A novel antimony catalyst for polyester condensation reactions is described comprising trivalent antimony having its valences occupied by dianion radicals of 1,2-diols and anion radicals or organic carboxylic acids. The molar ratio of antimony to dianion radical of 1,2-diol to anion radical of organic carboxylic acid is 1:1:1. The antimony compound is prepared by reacting a mixture of a 1,2-diol and a trivalent antimony reactant represented by the formula;   wherein Sb is antimony, R1 is an anion radical of an organic carboxylic acid; and R2 is selected from the group consisting of anions of alcohols, anions of organic carboxylic acids and mixtures thereof.

United States Patent [1 91 Loeffler Aug. 12, 1975 TRIVALENT ANTIMONYCATALYST [75] Inventor: Otto Ernest Loeffler, Rahway, NJ.

[73] Assignee: NL Industries, Inc., New York, NY.

[22] Filed: Aug. 24, 1973 211 Appl. No.: 391,121

[52] US. Cl 260/414; 252/431 C; 260/75 R; 260/446 [51] Int. Cl.C07f'9/90 [58] Field of Search 260/446, 75 R, 414

[56] References Cited UNITED STATES PATENTS 1,688,964. 10/1928 Hahl260/446 1,701,234 2/1929 Hahl 260/446 2,221,831 11/1940 Brown et a1.260/446 2,226,530 12/1940 Brown et a1. 260/446 2,466,019 4/ 1949Friedheim 260/446 3,484,410 12/1969 Lazarus et a1. 260/446 OTHERPUBLICATIONS Mann, The Heterocyclic Derivatives of Phosophorus, Arsenic,Antimony and Biomuth Interscience Publishers, N.Y., N.Y., 1970, p. 618.

Primary Examiner-Arthur P. Demers 57 ABSTRACT A novel antimony catalystfor polyester condensation reactions is described comprising trivalentantimony having its valences occupied by dianion radicals of 1,2-diolsand anion radicals or organic carboxylic acids. The molar ratio ofantimony to dianion radical of 1,2-diol to anion radical of organiccarboxylic acid is 1:1:1. The antimony compound is prepared by reactinga mixture of a 1,2-diol and a trivalent antimony reactant represented bythe formula;

wherein Sb is antimony, R is an anion radical of an organic carboxylicacid; and R is selected from the group consisting of anions of alcohols,anions of organic carboxylic acids and mixtures thereof.

9 Claims, No Drawings 1 TRIVALENT ANTIMONY CATALYST BACKGROUND OF THEINVENTION This invention is concerned with a novel trivalent antimonycompound useful as a catalyst in the manufacture of polyesters such aspolyethylene tercpthalate from dimethyl terepthalate and ethyleneglycol. In addition, this invention is also concerned with a novelprocess for the preparation of said trivalent antimony catalyst.

In the past, many trivalent and pentavalent antimony compounds have beenused as catalysts in the production of polyesters such as polyethyleneterepthalate. Among these antimony compounds are antimony trioxide,antimony pentoxide, alkyl antimony compounds,

. aryl antimony compounds and the like. In fact, almost such as Zn (OAc)2H O. The mixture is heated to remove an alcohol from the diester withthe formation of an ester-exchange product, diglycol terepthalate. Anantimony catalyst, such as those mentioned above is then added to thereaction mixture, and the temperature is raised to from 250 to 300Cunder reduced pressure to effect polycondensation and form thepolyethylene terepthalate.

The amount of soluble antimony provided by the catalyst is an importantcriterion for judging an effective antimony catalyst. It is oftendesirable to utilize an antimony catalyst which provides a high degreeof soluble antimony in the ethylene glycol reaction medium. This ,highantimony solubility aids in the activity of the catalyst which in turncauses the reaction to proceed at a faster rate. For example, antimonytrioxide which is a frequently used catalyst for the production ofpolyethylene terepthalate is relatively inexpensive but provides verylow antimony solubility in the ethylene glycol reaction medium. Antimonyglycoloxide, Sb- (OCH C- H O),,, another widely used catalyst, isrelatively expensive and provides from only 1.5 to 1.7% soluble antimonyat 80C. The antimony catalyst of this invention, however, provides from5.1 to 5.6% soluble antimony at 80C which is marked improvement over theprior art. catalysts mentioned above making it particularly desirableforcommercial production of polyethylene terepthalate. The antimonycatalyst of this invention can be produced cheaply by virtue of simpleprocessing stepsinvolving short reaction times and inexpensive {startingmaterials. I

It is an object of this invention to describe a novel antimony catalystfor the production of polyethylene terepthalate which provides a highdegree of soluble t antimony in' the polyethylene terepthalate reactionme- Idiumf.

A still further object is to describe a novel and inexpensive processfor the production of said trivalent antimony catalyst.

SUMMARY OF THE INVENTION The trivalent antimony compound of thisinvention comprises a mixed antimony l,2-diolate and carboxylate whereinthe valences of antimony are occupied by dianion radicals of l,2-diolsand carboxylate anion radicals. The molar ratio of antimony to dioldianion radical to carboxylate anion radical is l:l:l. The term l,2-diol as used herein is meant to describe an organic dihydroxy compoundwherein the hydroxyl groups are bonded to adjacent carbon atoms.

Although the structural formula is not known accurately, the X- ra'ydiffraction pattern, infra-red absorption spectra and, elementalanalysis have been used to supplement the characterization of thesecompounds.

Some of the possible chemical structures which may describe the antimonycatalyst based on spectral data and elementalanalysis, are representedby the following formulae:

wherein R is an anion radical of an organic carboxylic acid. Thel,2-diol dianion portion is represented by the formula [-O--CH CH O]-which is the dianion radical of ethylene glycol. In all formulae shownabove the ratio of antimony to l,2-diol dianion radical to carboxylateanion radical is 1:1:1.

An example of a typical antimony compound is a mixed trivalent antimonyethylene glycoloxide and acetate; wherein and the l,2-diol portion isethylene glycol dianion radical, -[OCH -CH -O]-.

This antimony compound exhibits and X-ray diffraction pattern withcharacterizing d-spacings in the vicinity of l 1.01 5.43, 6.27 and 3.60Aand has major infrared absorption peaks as 1720, 1375 andl570,reciprocal centimeters. The compound has the following elementalanalysis; about l6.8i 1 weight percent carbon;

reactant antimony triacetate, and for antimony glycoloxide which is apossible product in the reaction of antimony triacetate with molarexcesses of ethylene glycol at elevated temperatures as described in mycopending US. application Ser. No. 391,122, now US. Pat. No. 3,833,630,

TABLE l X-RAY I lNl-RA-Rlil) Elemental Analysis DIFFRACIION (MAJORtl-Spucings) (Major Peaks) (weight percent) Calculated 'l'hcorcticnlAntimony 'Iriucetutc Amorphous 1720 cm- C 24.06 1637 cm-' H 3.01 1338 cmSh 40.5 Sb 40.70 Antimony (il \OlUXlLlC 3.22 A 1630 cm 17.50 C 17.036.47 A 1450 cm- H 3.50 H 2.84 (.35 A 1100 cm Sb 58.5 Sli=-57.(\ 7.511 A'l'rivulent Antimony l 1.01 A 1720 cm-' C 168:1 Compound 5.43 A" 1375 cmH 3.2: .4 (R =CH:,) 6.27 A I570 cm' Sh:

a. reacting a mixture of equimolar ratios of a 1,2-diol and a trivalentantimony reactant represented by the formula;

wherein Sb is antimony, R is an anion radical of an or ganic carboxylicacid; and R is selected from the group I clude ethylene glycol,l,2-propane diol, 3-chlor o-l, 2

propane diol and mixtures thereof. v

The reaction mixture should preferably contain a solvent to aid thefluidity of the mixture and the recovery of the formed trivalentantimony catalyst. Such solvents must be inert to the antimony reactantand the formed trivalent antimony compound and be capable of dissolvingthe 1,2-diol and the antimony starting ma- As Table 1 shows, X-raydiffraction patterns, infrared spectral data and elemental analysis ofthe trivalent antimony compound of this invention compared with antimonytriacetate and antimony glycoloxide indicate vast differences instructure and composition.

Considerations of elemental analysis of the trivalent antimony compoundand the relative stiochiometry of the 1,2-diol and trivalent antimonyreactant affords a basis for postulation of the structure of thetrivalent antimony compound as represented by Formulae 1-4.

The above identified antimony compound does not restrict the scope ofthis invention however. Homologous antimony compounds wherein R,comprises anion radicals of higher organic carboxylic acids such aspropionic, butyric, hexanoic, octanoic, 2-ethyl-hexanoic and higher andmixtures thereof are within the scope of this invention. In addition,other 1,2-diols may also be employed in place of ethylene glycol as forexample 1,2-alkane diols substituted with alkyl groups such as1,2-propane diol, 1,2-butane diol or 1,2-alkane diols substituted withalkyl halides, such as 3-chlorol, 2- propane diol. The 1,2-diol can besubstituted with -many other radicals including sulfur-containing,nitroter ial. Among such solvents include alcohols such as' a novelprocess for preparing said antimony glycoloxide and is also part of thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The Xray diffraction data,infra-red spectral data and elemental analysis for a trivalent antimonycompound of this invention wherein R =O CCl-l and the l,2-diol isethylene glycol are repeated again in Table 1 below together with thepreferred trivalent antimony gen-containing or oxygen-containingradicals and may also be cycloalkane diols such as 1,2-cyclohexane diolor aromatic diols such as orthohydroxy phenol.

In preparing the trivalent antimony compound the 1,2-diol and antimonyreactant are combined with stir- 7 ring to form a viscous reactionmixture. The amount of diol used must be at least one molar with respectto the amount of antimony reactant. Preferably, an excess of diol isused to insure complete reaction. The reaction mixture is heated tobetween 40C and 120C and preferably between 60 and C. Temperatures aboveC for extended periods of time should be avoided since no appreciablegain reaction rate is achieved. There is also the added danger ofdecomposing the antimony compound or antimony reactant at elevatedtemperatures. If alcoholic solvents are employed in the reaction at hightemperatures, esters may be formed by the reaction of the alcohols withthe organic carboxylic acid replaced inthe antimony reactant. The timepreferred to complete the reaction varies with the temperaturesemployed. However, at temperatures between 60 and- 100C the reaction iscompleted in 15 to 20 minutes. Reaction times greater than 1 hour athigh temperatures should be avoided.

A solvent is preferably employed in this process as hereinbeforementioned. These solvents provide a fluid medium for the reaction andaid in the recovery of the trivalent antimony compound because theantimony compound is insoluble in these solvents and it precipitatestherefrom as it is formed. The amount of solvent is not critical butshould be added in an amount to insure efficient mixing of thereactions. Usually from 2 g to 3 g of solvent is added for each gram of1,2-diol.

Antimony glycoloxide, Sb (O-CH CH -O) can be produced by treating atrivalent antimony compound of this invention wherein the 1,2-dioldianion radical is ethylene glycol dianion radical with V2 molarequivalents or more of ethylene glycol at high temperatures (80C orabove) for periods of time in excess of 1 hour.

The trivalent antimony compound can be recovered as for example byfiltration or centrifugation of the reaction mixture followed by solventremoval and drying of the product. If no solvent is utilized during thereaction, it can be added after the reaction is completed to aid in therecovery of the product as described below.

reacting an appropriate antimony trialkoxide with mixtures of organiccarboxylic acids.

Alcoholate anion radicals for R having from 1 to about carbon atoms arepreferred to give optimum results in yield and rate of reaction.Alcoholate anion radicals having greater than 10 carbon atoms are lessdesirable to employ in the antimony reactant since they becomeincreasingly more difficult to replace by the 1,2-diol as the number ofcarbon atoms increase.

It is preferred to use antimony reactants wherein the organic carboxylicacid anion, R contains from 1 to about 10 carbonatoms'. Higher organiccarboxylic acid anions although useful in this invention are replacedless easily by the 1,2-diol than the carboxylic acid anion radicalscontaining from 1 to 10 carbon atoms.

In order to more fully describe the instant invention the followingexamples are given;

EXAMPLE 1 This example illustrates a laboratory preparation of thetrivalent antimony compound using antimony triacetate as the trivalentantimony reactant and ethylene glycol as the 1,2-alkane diol. Methylethyl ketone employed as a solvent.

To a 500 ml. reaction flask equipped with stirrer, thermometer andreflux condensor was added 105.8 g.

(0.354 m) of antimony triacetate, 28 g. (0.452 m) of ethylene glycol and77 g. of methyl ethyl ketone.

The mixture was heated to (97C) under a stream of nitrogen for minutes.The mixture was cooled and then filtered through a Buchner funnel anddried in a vacuum oven at room temperature. The trivalent antimonycompound after drying weighed 78.6 g. Yield was 92%. The X-raydiffraction pattern and infra-red spectra were consistent with thosegiven Table l.

Elemental analysis: Observed C; 168i] H; 3.4i0.4

Sb; 50.3-30.5. The compound had the following solubil- After prolongedstanding (2 weeks) a small amount of solid precipitated which wasantimony glycoloxide, Sb,(OCH CH -O);,.

EXAMPLE 2 This example illustrates a large-scale pilot plant productionof the trivalent antimony compound employing methanol as a solvent.

To a 50 gallon Pfaudler reactor was added 185 lbs. of antimonytriacetate, lbs. of ethylene glycol and 151 lbs. of methanol. Themixture was stirred and heated at 72-75C for 20 minutes under a nitrogenblanket. The reaction mixture was cooled to room temperature andcentrifuged through a Sharples centrifuge and the supernatant liquidremoved. Analysis of this product was substantially the same as inExample 1. When this product was treated with 2 molar equivalents ofethylene glycol at C for l hour, antimony glycoloxide was produced.

EXAMPLE 3 col with a trivalent antimony reactant represented by theformula;

A 50 ml. reaction flask equipped with stirrer, thermometer and refluxcondensor was charged with 17 g.

(0.05 m) of antimony tributoxide, Sb(O(CH CH' To this was added 3.0 g(0.05 m) of acetic acid. Next, 3.1

g (0.05 m) of ethylene glycol was added to the flask together with 30.0g of methyl ethyl ketone. The mixture was heated to reflux (C) for 15minutes under a stream of nitrogen. The mixture was cooled to roomtemperature and filtered through a Buchner funnel. The recovered productwas then dried in a vacuum oven at room temperature. The trivalentantimony compound after drying weighed 13.2 g. The infra-red spectrumtaken of the product was consistent with the spectrum given in Table 1.When this productwas treated with 2 molar equivalents of ethylene glycolat 80C for 1 hour, antimony glycoloxide was produced.

EXAMPLE 4 This example illustrates the preparation of a trivalentantimony compound comprising a mixed antimony ethylene glycolate andbutyrate made by reacting ethylene glycol with antimony tributyrate. i

To a 250 ml reaction flask was charged 25.6 g (.067m) of antimonytributyrate, Sb(O C(CH CH;,)- To this was added 19.24 g (0.31 m) ofethylene glycol followed by 70 ml of methyl ethyl ketone. The mixturewas heated to 90C for 15 minutes under a stream of 5 nitrogen and thencooled to room temperature. The infra-red spectrum of the dried productwas similar to the infra-red pattern of Examples 1, 2 and 3 except thata more intense peak at 1375 cm -1 was present indicating increased .(CHgroupings.

EXAMPLE 5 This example illustrates the preparation of a trivalentantimony compound made by reacting ethylene glycol with an antimonyreactant represented by the formula;

ocn cr-ncl-r cn,

ll Sb -O c cn,

amples l, 2 and 3. 5

EXAMPLE 6 This example illustrates the preparation of a trivalentantimony compound containing a substituted 1,2- alkane diol dianionradical and acetate anion radical. 40

The 1,2-alkane diol used was 3-chlor'o-l,2-propane diol.

The procedure of Example 1 was followed except 300 ml of methyl ethylketone and 22.0 g (0.2 m) of 3- chloro-1,2-propane diol was added to 0.1mole antimony triacetate reactant instead of ethylene glycol.

After working up the product it was found that the needle'like crystalshad the following analysis:

Elemental Analysis (wt.

Sb 4] .04 C 12.72

Major Infra-Red Peaks 1 1 l708cm and 1365 cm EXAMPLE 7 7 Preparation ofpolyethylene terephthalate. Exactly g of dimethyl terepthalate, 750 g ofethylene glycol and 0.9 g of zinc acetate dihydrate were heated to atemperature of 190C under an atmosphere of nitrogen. The reaction wascontinued for 3, hours collecting 297 g of methanol. This intermediate(100 g) was added to a 200 ml stainless steel flask containing thetrivalent antimony catalyst of Example 1 in an amount sufficient toprovide 0.025 g atoms of antimony. The

temperature was raised to 28()290C under a pressure of 0.15 mm Hg. Thematerial was heated for 3 hours under these conditions and the polymerrecovered.

What is claimed is:

1. A trivalent antimony catalyst having the valences of antimonyoccupied by dianion radical of a 1,2- alkane diol and organiccarboxylate anion radical, said carboxylate anion radical contianingfrom 1 to 10 carbon atoms, wherein the molar ratio of antimony todianion radical of 1,2-alkane diol to organic carboxylate anion radicalis 1:1:1, and wherein said dianion radical of a 1,2-alkane diol isselected from the group consisting of ethylene glycol dianion,1,2-propane diol dianion, 3-chloro-1 ,2-propane diol dianion, 1,2-butanediol dianion, and mixtures thereof.

2. The catalyst of claim 1 wherein said organic carboxylate anionradical is selected from the group consisting of acetate anion, butyrateanion, 2-ethyl hexanoate anion and mixtures thereof.

3. A trivalent antimony catalyst having the valences of antimonyoccupied by dianion radical of ethylene glycol and acetate anion radicalwherein the molar ratio of antimony to dianion radical of ethyleneglycol to acetate anion radical is 1:1 :1 said catalyst exhibiting anX-ray diffraction pattern with characterizing dspacings in the vicinityof l 1.01, 5.43, 6.27 and 3.60 Angstroms, and having major infra-redabsorption peaks at 1720, 1375 and 1570 reciprocal centimeters.

4. A process for the preparation of the trivalent antimony catalyst ofclaim 1 comprising;

a. heating a mixture of about equimolar proportions of a 1,2-alkane diolselected from the group consisting of ethylene glycol, 1,2-propane,1,2-butane, 3-chloro-1,2-propane, and mixtures thereof, and a trivalentantimony reactant; said trivalent antimony reactant represented by theformula;

wherein Sb is antimony, R is an anion radical of an organic carboxylicacid having form 1 to 10 carbon atoms and R is selected from the groupconsisting of anion radicals of alcohols having from 1 to 10 carbonatoms, anion radicals of organic carboxylic acids having from 1 to 10carbon atoms and mixtures thereof; and

b. recovering a trivalent antimony catalyst from said mixture.

5. The process of claim 4 wherein saidmixture further comprises asolvent.

6. The process of claim 4 wherein said mixture is heated from 40C to C.

7. The process of claim 4 wherein said mixture is heated for less than 1hour.

8. A process for the preparation of antimony glycoloxide which comprisesheating a mixture of ethylene glycol and a trivalent antimony compound;said trivalent antimony compound having the valences of antimonyoccupied by dianion radical of ethylene glycol and organic carboxylateanion radical wherein the molar ratio of antimony to dianion radical ofethylene glycol to organic carboxylate anion radical is 1:1:1.

9. The process of claim 8 wherein said organic carboxylate anion radicalis selected from the group consisting of acetate, butyrate, 2-ethylhexanoate and mixtures thereof.

1. A TRIVALENT ANTIMONY CATALYST HAVING THE VALENCES OF ANTIMONYOCCUPIED BY DIANION RADICAL OF A 1,2-ALKANE DIOL AND ORGANIC CARBOXYLTEANION RADICAL, SAID CARBOXYLATE ANION RADICAL CONTAINING FROM 1 TO 10CARBON ATOMS, WHEREIN THE MOLAR RATO OF ANTIMONY TO DIANION RADCAL OF1,2-ALKANE DIOL TO ORGANIC CARBOXYLATE ANION RADICALS IS 1:1:1, ANDWHEREIN SAID DIANION RADICAL OF A 1,2-ALKANE DIOL IS SELECTED FROM THEGROUP CONSISTING OF ETHYLENE GLYCOL DIANION, 1,2-PROPANE DIOL DIANION,3-CHLORO-1,2-PROPANE DIOL DIAMION, 1,2-BUSTANE DIOL DIANION, ANDMIXTURES THEREOF.
 2. The catalyst of claim 1 wherein said organiccarboxylate anion radical is selected from the group consisting ofacetate anion, butyrate anion, 2-ethyl hexanoate anion and mixturesthereof.
 3. A trivalent antimony catalyst having the valences ofantimony occupied by dianion radical of ethylene glycol and acetateanion radical wherein the molar ratio of antimony to dianion radical ofethylene glycol to acetate anion radical is 1:1:1; said catalystexhibiting an X-ray diffraction pattern with characterizing d-spacingsin the vicinity of 11.01, 5.43, 6.27 and 3.60 Angstroms, and havingmajor infra-red absorption peaks at 1720, 1375 and 1570 reciprocalcentimeters.
 4. A process for the preparation of the trivalent antimonycatalyst of claim 1 comprising; a. heating a mixture of about equimolarproportions of a 1,2-alkane diol selected from the group consisting ofethylene glycol, 1,2-propane, 1,2-butane, 3-chloro-1,2-propane, andmixtures thereof, and a trivalent antimony reactant; said trivalentantimony reactant represented by the formula;
 5. The process of claim 4wherein said mixture further comprises a solvent.
 6. The process ofclaim 4 wherein said mixture is heated from 40*C to 120*C.
 7. Theprocess of claim 4 wherein said mixture is heated for less than 1 hour.8. A process for the preparation of antimony glycoloxide which comprisesheating a mixture of ethylene glycol and a trivalent antimony compound;said trivalent antimony compound having the valences of antimonyoccupied by dianion radical of ethylene glycol and organic carboxylateanion radical wherein the molar ratio of antimony to dianion radical ofethylene glycol to organic carboxylate anion radical is 1:1:1.
 9. Theprocess of claim 8 wherein said organic carboxylate anion radical isselected from the group consisting of acetate, butyrate, 2-ethylhexanoate and mixtures thereof.